No one knows who was the first one to think of riding bikes in the mountains. The   (1)   just seemed fun. The first mountain bikers were from Colorado and Northern California. They had   (2)   done their riding on main roads. Then some of the cyclists   (3)   the mountains nearby. Why not   (4)   on the paths there, too?

The   (5)   was that racing bikes weren’t strong enough. For   (6)   riding, you need a   (7)   bike. It has to have wide tires to hold onto dirt roads, and the bike itself has to be higher off the ground. Stores didn’t   (8)   that kind of bike then, so the cyclists   (9)   their own. The cyclists found   (10)   bikes that had once been popular by   (11)   second-hand markets. They cleaned them up, added strong handlebars(把手), put on heavy-duty tires and made other  (12)   .

Cyclists in different areas heard about mountain biking, and the movement     (13)   . Soon the mountain bikers were teaching themselves tricky   (14)   , such as jumping their bikes over rocks and stones.

In a short time, mountain bikers raced each other down mountain passes. Sometimes they took it   (15)   and just enjoyed the views---- as if they were doing a hike on a bike. To   (16)   injuries, they began wearing safety equipment.

One winter when there was no snow, mountain bikers in Crested Butte, Colorado,   (17)    a “Fat Tire Festival!” Bicycle companies guessed the sports would become very   (18)  . Almost as soon as the companies began producing them in large numbers, mountain bikes became America’s   (19)   type of bike. They’re comfortable and fun to ride,   (20)    you never ride them off-road, away from main roads.